This application claims priority from Korean Patent Application No. 2002-54327, filed on Sep. 9, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a light emitting diode, and more particularly, to a light emitting diode whose light emission is enhanced by appropriately varying the size of its p-type electrode.
2. Description of the Related Art
Light emitting diodes are widely known as a device used for data transmission in the optical communications field, for data recording and reproduction in compact disc players (CDPs) or digital versatile disk players (DVDPs), and for outdoor display.
FIG. 1 is a sectional view of a conventional light emitting diode (LED) having an InGaN—AlGaN heterojunction structure. Referring to FIG. 1, an n-GaN layer 3 is formed on a sapphire substrate 1 with a GaN buffer layer 2 interposed therebetween. An In0.06Ga0.94N active layer 5, where light is generated, and p-Al0.15Ga0.85N layer 6 are formed on the n-GaN layer 3. The sequential deposition of the n-GaN layer 3, the In0.06Ga0.94N active layer 5, the p-Al0.15Ga0.85N layer 6, and the p-GaN layer 7 is followed by patterning to a depth in the GaN layer 3, and a n-type electrode 8 is attached to the n-GaN layer 3. A p-type electrode 9 is arranged on the p-GaN layer 3 and is electrically connected to an external power source (not shown) via a bonding pad 10, which is arranged to contact to an edge of the p-GaN layer 7.
Most conventional LEDs generate light of a blue or red wavelength range and emit the light toward the front side through a transparent p-type electrode. Conventionally, as illustrated in FIG. 1, the p-type electrode 9 is formed on the entire surface of the p-GaN layer 7 in order to emit light through a larger area. As the size of the p-type electrode 9 increases, driving voltage becomes lower, enabling stable light emission at a low current density.
FIGS. 2A and 2B illustrate examples of conventional light emitting diodes where a p-type electrode, a bonding pad, and a n-type electrode are arranged in different patterns. Reference numerals 8a and 8b denote n-type electrodes, reference numerals 9a and 9b denote p-type electrodes, and reference numerals 10a and 10b denote bonding pads. As shown in the photographs of FIGS. 2A and 2B, light is emitted through the entire surface of the p-type electrodes 9a and 9b occupying most of the surface of the light emitting diode.
However, in conventional 430-nm or less light emitting diodes, light emission tends to decrease with increasing area of the p-type electrode. Therefore, there is a need to appropriately adjust the size of the p-type electrode in light emitting diodes which emit light of these wavelengths, to increase light emission.